1. Field of the Invention
Embodiments of the invention generally relate to a method and apparatus for annealing metallic objects. More specifically, embodiments described herein relate to a method and apparatus for annealing elongated, tubular cases made of a metallic material, such as brass ammunition cartridges, or ammunition cases or casings.
2. Description of the Related Art
Annealing is a process where heat is applied to a metal in order to change the properties, such as strength and hardness, of the metal. Annealing is typically utilized to improve ductility, relieve internal stresses, and generally soften metals that have been hardened by working the metal and/or heat treatment. Proper annealing restores the properties of the metal to a near original or virgin state.
Ammunition cartridges or cases are made from brass which is subject to hardening during manufacture, use, and reloading of the cases. Commercially available cartridges are typically annealed during manufacture to include various hardnesses along the length of the case. For example, firearm cartridges typically include a base at a first end thereof where the primer is located and a mouth at a second end thereof where the projectile is held. In a properly annealed cartridge the mouth will have a greater ductility than the base. However, when the cartridge is used to discharge a projectile, heat is created which causes the case to expand and contract, thus hardening the case, and particularly, the mouth of the case. Reuse (i.e., reloading) of the case requires subsequent processing, such as sizing and trimming of the case, which may work-harden portions of the case. If the hardened portions of the case are not annealed, such as the mouth (or neck, in shouldered cases), the mouth may crack and render the cartridge unusable. Thus, annealing of the cases assures proper operation of the cartridge as well as extends the lifetime of the case for subsequent reuse.
Devices for annealing ammunition cases are commercially available; however, the commercially available devices suffer from some drawbacks. In one commercially available device, only a single case may be loaded and annealed at one time, which is time consuming and labor intensive. Other conventional devices typically hold multiple cases vertically in a turntable that rotates in a horizontal plane. The commercial devices do not include an automatic case loading device. Loading of the turntable is thus done manually to assure that the case is properly oriented in the turntable (e.g., mouth up/base down). This requires constant supervision by personnel during operation to ensure efficient throughput. Further, the horizontally oriented turntable devices are heavy and occupy a large footprint. Additionally, the conventional devices often require more than one heat source, which increases the cost of the annealing operation. While these conventional devices may be suitable for the occasional user, the devices are not desirable for commercial operations and/or frequent users.
Thus, there exists a need in the art for a method and apparatus for an annealing device capable of automatic loading of cases, high-throughput and requires a smaller footprint.